Now, researchers are also looking to see if the virus can spread from the eyes, like through tears.
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Hepatitis C virus, a related virus, can infect the human cornea and is transmitted by corneal transplants, the study said. “Our findings could offer valuable information to support time-sensitive public health decision-making at local, national, and worldwide levels”, Dr Kamran Khan, study author from St Michael’s Hospital in Toronto, told the BBC.
The study suggests that the eye could be a reservoir for the virus.
About one-third of babies infected with Zika in the womb have eye problems. Zika infections in pregnant women have been shown to cause microcephaly – a severe birth defect in which the head and brain are undersized – as well as other brain abnormalities. Although the researchers don’t know exactly how the virus is traveling from the blood to the eye, these new findings suggest why some infected adults develop conjunctivitis (redness and itchiness of the eyes) and, in rare cases, an eye infection called uveitis (that can be serious and lead to vision loss). Even if the sad salty tears of humans turn out not to be infectious, the researchers’ detection of live virus in the eye and viral RNA in tears still has practical benefits.
The scientists cautioned that more studies are needed to determine if tears could spread the Zika virus in people.
The immune system is less active in the eye in order to avoid accidental damage to sensitive tissues responsible for vision when the body is fighting an infection.
“The advantage to using the eye is that your dosing requirements are very small and you don’t have to worry as much about effects of larger dosages of therapeutic agents on the rest of the body, such as liver toxicity”, says Apte, who is also a professor of developmental biology and of medicine.
In the lab the researchers found live virus in the eyes after seven days, though they were unable to confirm the method by which the virus traveled there; perhaps by crossing the blood-retina barrier that separates the eye from the bloodstream or along the optic nerve that connects the brain and the eye, or maybe another way altogether.
The research appears in the journal Cell Reports.
It has been reported that “currently, over 65 countries and territories” around the world are “battling transmission of the Zika virus”.
Since previous year, 69 countries and territories reported evidence of Zika infection via the Aedes aegypti mosquito – the main mode of transmission. However, last month, two neighborhoods in the Miami area reported cases of locally acquired infection.
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Also last week, the head of the U.S. Centers for Disease Control and Prevention said federal funds to combat the Zika virus were almost gone and there would be no money to fight a new outbreak unless Congress approves more funding.
